1. Field of the Invention
The present invention relates to an image forming apparatus, and more particularly to an image forming apparatus, such as an electrophotographic copying machine, comprising a laser scanning unit.
2. Description of Related Art
Image forming apparatuses, such as electrophotograhic copying machines and printers, generally comprise a laser scanning unit for illuminating a photosensitive member with a laser modulated in accordance with image data. In such a laser scanning unit, a dust-poof glass is provided to a radiation window so that toner and dust particles suspended in the air inside a machine will not enter into the unit. However, it is likely that these particles stick to the surface of the dust-proof glass, and in this case, the picture quality of a formed image is lowered (white stripes are seen in a formed image). Especially when the laser scanning unit is located under a processing unit including a photosensitive member, the trouble caused by the adherence of particles to the dust-proof glass is notable.
In order to avoid the trouble, conventionally, Japanese Patent Laid-Open Publication No. 2007-72321 suggests that a cleaner be provided in the laser scanning unit. Japanese Patent Laid-Open Publication No. 2007-72321 also suggests that the cleaner be kept out of contact with the dust-proof glass when the cleaner is in a stand-by position, while the cleaner be moved to clean the surface of the dust-proof glass at desired times. However, when the cleaner is supported by a housing of the laser scanning unit, even if the cleaner is kept out of contact with the dust-proof glass, the housing of the laser scanning unit may be deformed by the load of the cleaner, which may cause a problem that the optical characteristics of laser radiation are lowered.